1. Field of Invention
This invention relates to amplifiers. Specifically, the present invention relates to broadband switching-mode amplifiers.
2. Description of the Related Art
High Power Amplifiers (HPA's) are employed in various demanding applications including telecommunications, avionics systems, digital radio transmitters, military targeting and tracking, and transceiver modules for phased array radar systems. Such applications require efficient, lightweight, compact, cost-effective, high power amplifiers. Cost, size, weight, and efficiency considerations are particularly important in space-based transceiver applications, such as space-based phased array radar systems, where any extra size, weight, or HPA inefficiencies can dramatically increase overall mission cost.
Conventional amplifiers are often either Class A, B, A-B, or C amplifiers that operate at a Power Added Efficiencies (PAE's) of less than 50% at X-band, which is the frequency band between 8 and 12 GHz. Internal power dissipation due to overlapping voltage and current waveforms at the amplifier's active device terminals and inefficiencies in output matching network baluns often limit PAE to below 50%, which is undesirably low for various applications, such as space-based radar.
These conventional amplifiers often employ complex microwave baluns that have limited bandwidth and high insertion loss at X-band and that are difficult to integrate with accompanying chipsets. Attempts to improve HPA efficiency and applicability via GaAs Monolithic Microwave Integrated Circuit (MMIC) technology have produced limited results. Generally, wideband amplifiers trade bandwidth for relatively high insertion loss and lower PAE. Currently, highly efficient microwave power amplifiers that operate at PAE's above 60% at frequencies over 2 GHz are unavailable.
Hence, a need exists in the art for a highly efficient, compact, and cost-effective, wideband monolithic HPA capable of operating at RF, X-band, and/or S-band that is easily integrated with various chipsets, including GaAs-based integrated circuits.